224 Dr. Marcet on an Aluminous Chalybeate Spring 



of the water, the h'on by prussiat of potash — the lime by oxalat of 

 ammonia — the alumine and magnesia by caustic potash, which, by 

 boiUng, re-dissolves the alumine and leaves the magnesia untouched. 



^Id method. To precipitate the iron and earths by subcarbonat of 

 ammonia. To evaporate the remaining clear solution to dr^mess, 

 and apply a red heat. To re-dissolve this saline residue, and eva- 

 porate the solution slowly, in order to discover any fixed alkaline 

 sulphat or muriat which may exist in the water. To boil in caustic 

 potash the precipitate containing the iron and earths, in order to 

 separate the alumine and silica. To dissolve the remaining mass 

 (supposed to contain iron, lime, and magnesia) in nitric acid, eva- 

 porate to dryness, and apply a red heat, in order to render the per- 

 oxyd of iron thus formed insoluble in acid. To add to the mass 

 minutely pulverized, nitric or acetic acid, as either of these acids 

 will only dissolve the lime and magnesia^ which may be separately 

 obtained by their respective reagents. And lastly, to ascertain the 

 quantity of oxyd of iron^ supposed to have been left untouched by 

 the acid. 



2>d method. To precipitate from another portion of water, the 

 iron, lime, alumine and silica, by a solution of neutral carbonat 

 of ammonia, which reagent retains the magnesia in solution. To 

 boil the precipitate in caustic potash, which takes up the alumine 

 and silica. To re-dissolve in muriatic acid the residue not taken up 

 by potash, which consists of lime and iron — separate the iron by 

 pure ammonia, and the lime by oxalat of ammonia.* Precipitate the 

 magnesia f from the clear solution by an alkaline phosphat. 



* It is necessary to precipitate the iron before the lime, whin)evcr any considerable 

 quantity of sulphat or muriat of iron is present. For oxalat of ammonia acts upon 

 solutions of iron, as will be fully explained under the head of sulphat of lime. 



i The magnesia might be equally, and perhaps more cunvcnleiUly separated, by 



